Mercury capture from natural gas by carbon supported ionic liquids: Synthesis, evaluation and molecular mechanism

Superiority of silica supported ionic liquids over other adsorbents in capturing elemental mercury (Hg-0) from flue gases has been recently reported. In this study, activated carbon, which is more economical than silica, was experimented as a solid support for ionic liquids (ILs) for gaseous Hg-0 removal. Four ILs were successfully coated on activated carbon. The carbon supported ionic liquids (CSILs) were characterized by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area analysis, field emission scanning electron microscopy, energy-dispersive X-ray, X ray-photoelectron spectroscopy and nuclear magnetic resonance. A continuous fixed bed flow reactor was used to examine the performance of CSILs in treating 20-35 ppm Hg-0 vapor at a gas flow rate of 60 mL/min. 1-Butyl-3-methylimidazolium chloride [Bmim] Cl coated activated carbon was the most reactive among CSILs studied and a powdered form of [Bmim]Cl coated activated carbon was able to uptake Hg-0 up to 23 mg/g and 60 mg/g with N-2 and CH4 as carrier gas, respectively. A molecular simulation was performed to investigate the molecular level interaction between the Hg-0 and the ILs to understand the effect of structural variations of the ILs on Hg-0 adsorption. The simulation reveals that the anion part of IL plays a major role in Hg-0 adsorption. Based on experimental results, a possible mechanism of Hg-IL interaction was elucidated; the imidazolium cation can form a complex with HgCl2 through the C2 hydrogen. (C) 2016 Elsevier Ltd. All rights reserved.